Liver is an important organ which participates in most of metabolisms and regulation thereof in a living body including metabolization of carbohydrate, protein, lipid, nucleic acid, vitamin, and hormone, production of bilirubin, secretion of bile, detoxification of endogeneous or exogeneous substances by oxidation, reduction and conjugation .degree. and excretion of them into bile or water-solubilization of them to accelerate excretion into urine. These functions may be damaged by toxic substances, medicines, alcohols, radiation and viruses to cause diseases such as medicinal liver diseases, alcoholic liver diseases, virus-caused hepatitis, fatty liver, jaundice, and the like. If these diseases are protracted, sometimes liver cirrhosis and liver cancer are developed.
However, medicines effective to cure these liver diseases have not yet been developed and at present, treatments therefor are only alimentotherapy and rest cure.
On the other hand, recently, it has been reported that pyrrolo quinoline quinone and pyrrolo quinoline quinone salts (hereinafter generically referred to as "PQQ") found as novel coenzymes of oxido-reductase inhibit liver diseases when administered intraperitoneally. (Japanese Patent Kokai No. 63-192717).
However, this activity was not observed when they are orally administered. (Watanabe et al, "Current Therapeutic Research", Vol. 44, No. 6, pp 896-901 (1988)). Furthermore, it has been clarified that "PQQ" has kidney toxicity (Watanabe et al, "Hiroshima J.Med. Sci.", Vo.1 38, No. 1, pp49-51 (1989)).
Thus, it has been desired to develop medicines which are low in toxicity, especially kidney toxicity, high in membrane permeability and can inhibit liver diseases not only through intraperitoneal administration, but also oral administration.